Incumbent Republican U.S. Congresswoman Lynn Morley Martin, of Illinois' 16th congressional district, decided to retire in order to run for the U.S. Senate. Manzullo ran for the seat, but lost in the Republican primary against State Representative John Hallock, Jr. 54%-46%.[4] In the general election, Hallock was defeated by Democrat John W. Cox, a city attorney.

1992

Manzullo ran for the 16th district again in 1992. He won the Republican primary defeating State Senator Jack Schaffer 56%-44%.[5] In the general election, he defeated the incumbent 56%-44%.[6]

1994–2006

During this time period, he was never challenged in the Republican primary. He won re-election every two years with at least 60% of the vote, and was completely unopposed in 1998.[7]

Illinois' congressional map was significantly altered after the 2010 census. Manzullo's district was significantly altered. While it retained his home in Ogle County, it lost most of its western portion to the 17th district. This included more than half of Rockford, which had anchored the district and its predecessors for a century and a half. The 16th was pushed well to the east, and now stretched from the Wisconsin border to the Indiana border, essentially wrapping around the collar counties. The new map placed him in the same district as the one-term incumbent of the old 11th district, fellow Republican Adam Kinzinger. Geographically, it was more Manzullo's district than Kinzinger's. The new 16th included roughly 44 percent of Manzullo's former territory and only 31 percent of Kinzinger's.[citation needed]

During his tenure in Congress, Manzullo authored 17 bills that were signed into law by the President and altered the direction of 18 other bills that also became law.[3] He also significantly influenced over 50 administrative actions by the Executive Branch through regulatory changes or alterations to internal policy.[3]

Manzullo spent most of his career working on issues related to manufacturing. He was featured on the cover of The Manufacturer because of his work with small business-related policy.[citation needed] Manzullo was the chairman of the Committee on Small Business from 2001 to 2007.[1] He held over sixty hearings during this time to investigate the phenomenon of corporate outsourcing. Manzullo has also worked on transportation issues. His ability to gain great funding for highway improvements within his district has given him somewhat of a reputation as a pork barreller. He authored a law that requires clinics to report instances of child abuse. Manzullo co-founded and co-chaired the bipartisan House Manufacturing Caucus and also served as a co-chair of the House Automotive Caucus.[3]

In November 2009, Manzullo was criticized by some constituents for calling [Islam] a “savage religion.” He was referring to the religion of the detainees at the Guantanamo, Cuba prison that are being considered for transfer to a Thomson, Illinois prison located in his district. He later apologized for the comment, saying that he was not referring generally to Islam, but to terrorists who "believe and practice a violent, anti-modernity version of Wahhabism in which they seek to impose a new caliphate.”[13]

During his time in Congress, Manzullo worked avidly to ensure "the safety of the American people".[14] He consistently supported the interests of the American Security Council Foundation and the Center for Security Politics.[15] At one point, Manzullo worked on an appeal to President Barack Obama to forgo his plan to move over 200 Taliban and al Qaeda terrorist suspects from Guantanamo Bay to northern Illinois for detainment.[14][16] He instead advocated for the creation of a new federal prison, the Thomson Correctional Facility, as a new hub in the already vastly over capacity prison system.[14][17]

To fund his campaigns for re-election, Manzullo receives financing from a number of contributors, foremost among them Honeywell International, which donated $10,000 towards his last election.[19] He has also received amounts of $5,000 or more from New York Life Insurance, American Society of Anesthesiologists, AFLAC Incorporated, and the American Bankers Association.[19] In total, 58% of his funds were drawn from private sources, and 40% from PAC contributions; none of his own money is used to finance his campaigns.[19][20]